Benzoic Acid Solution

Benzoic Acid	50 g
Propylene Glycol	750 mL
Purified Water, freshly boiled and cooled	Sufficient to produce 1000 mL

The following directions apply.

Dissolve the Benzoic Acid in the Propylene Glycol and add sufficient Purified Water, in small quantities and with constant stirring, to produce 1000 mL.

4.75 to 5.25% w/v.

A. To 5 mL add 30 mL of 1m sulfuric acid and extract the precipitated acid with three 25-mL quantities of petroleum spirit (boiling range, 40° to 60°). Wash the combined extracts with three 25-mL quantities of water, filter through absorbent cotton and evaporate to dryness. The infrared absorption spectrum of the residue, Appendix II A, is concordant with the reference spectrum of benzoic acid (RS 025).

B. Melting point of the residue obtained in test A, about 121°, Appendix V A.

1.045 to 1.055 g, Appendix V G.

To 10 mL add 20 mL of ethanol (96%) previously neutralised to phenolphthalein solution R1 and titrate with 0.1m sodium hydroxide VS using phenolphthalein solution R1 as indicator. Each mL of 0.1m sodium hydroxide VS is equivalent to 12.21 mg of C₇H₆O₂.